Axial flow fans are commonly used in cooling systems for engines of vehicles. Such fans consist of a hub with a number of blades extending substantially radially from said hub to a tip region. The shape of the blades is such that as the fan itself is rotated, air is caused to move axially according to the direction of the rotation of the fan. It would be understood by those skilled in the art that axial flow fans impart rotational components to the air which they move, and this creates turbulence effects which can both reduce efficiency and increase the noise from the u se of the fan.
It is known to use so-called "stator devices" in association with such axial flow fans, which stator devices are intended to straighten the air flow resulting from the fan. Such stator devices are static arrangements of blades or other members which "break up" the rotational components of air movement and which deflect the air towards a more axial flow path.
Axial flow fans in engine cooling systems are disposed within a so-called shroud which guides the air from or to a vehicle heat exchanger such as a radiator and which may also guide the air to or from a condenser of a vehicle air conditioning system.
Motion of the vehicle causes air to be passed through the radiator and/or air conditioning condenser but under certain circumstances is necessary to provide further air movement and this is effected by the movement of the fan. It is desirable to use a high efficiency fan due to the need to reduce fuel consumption as far as possible and also due to the fact that inefficiencies of the fan tend to give rise to higher ambient noise which is undesirable in modern vehicles.
Modern engine fans are driven by electric motors, and the motors themselves are supported within an opening of the shroud by a number, commonly three, of arms which depend from the peripheral wall of the shroud to a support ring which serves to support the motor. Such supports are supplemented in known stator arrangements by a number of additional radially-extending members which are curved in cross-section, or otherwise shaped in the axial direction so as to generally straighten the motion of the air from the fan. A number of problems has been found to exist in the prior art. Specifically, due to the axially packaging constraints, the axial chord of the stator members is too small to provide efficient straightening of the air flow. Furthermore early flow separation may occur on the stators which substantially increases the drag and thus reduces the aerodynamic efficiency of the stator assembly itself.
It would be possible to overcome these limitations by increasing the camber of the stator profile, but this would limit the working range of the fan system to an undesirable extent.